1. Field of the Invention
The present invention relates to a liquefied gas dispensing nozzle for flowing or dropping liquefied gas to a container, and to a dispensing apparatus equipped with said nozzle for dispensing the liquefied gas to a container.
2. Discussion of the Background
Generally, in the customary way, tight sealing is executed by seaming a can lid on an opening portion of a can, subsequently to dispense a little amount of inert and extremely cold liquefied gas which vaporizes at room temperature (from 20° C. to 25° C.) and increases its volume substantially, such as liquid nitrogen or liquefied argon on the liquid level in the beverage-filled can, during a filling and packing in the can of a non-carbonated beverage, i.e., a coffee, a tea, a green tea, an isotonic drink, a lactic acid drink, a fruit juice, a beverage containing a fruit juice and so on, where the can has a thin plated trunk wall such as a drawn and ironed can. This is intended to prevent the can from a deformation due to external pressure by means of raising internal pressure of the sealed can, and to prevent the beverage from deterioration in the can by means of substituting the air in a head space (a space of an upper portion of the beverage) of the can with the inert gas so as to reduce the amount of remaining oxygen.
There are several types of liquefied gas dispensing apparatuses for such an application and those may be divided roughly in two types, such as a type of injecting the liquefied gas with dropping (i.e., flowing intermittently) into the can, and a type of dispensing the liquefied gas with flowing continuously. The former mentioned so-called dropping type injection apparatus is disclosed in the specification of U.S. Pat. No. 4,407,340, and the latter mentioned so-called flowing type dispensing apparatus is disclosed in the specifications of U.S. Pat. Nos. 4,703,609 and 4,471,627 for example.
Those dispensing apparatuses are constructed to drop or to flow the liquefied gas out of a nozzle. It is necessary for the flow rate of the liquefied gas flown out of the nozzle to be adjusted to the speed of canned product manufacturing line, however, the speed of canned product manufacturing line is varied continuously, or adjusted subtly in recent days. One example of a liquefied gas dispensing apparatus, which can vary the flow rate of the liquefied gas flowing out of the flowing nozzle of the liquefied gas dispensing apparatus per unit of time continuously and steplessly, complying with the stepless speed change of canned product manufacturing line, is disclosed in Japanese Patent Laid-Open No. 10-250711 (JP 10-250711).
The liquefied gas dispensing apparatus disclosed in JP 10-250711 has a nozzle which comprises a cylinder, and a plug to be inserted in sliding arrangement into the cylinder and to be moved in the axial direction as its main components. A number of slit portions are formed in parallel with the axial direction, on the inner circumferential face of the cylinder which contacts with the outer circumferential face of the plug. A depth of each slit portion decreases from an upper end to a lower end. Accordingly, an opening dimension of the nozzle becomes lager continuously as the plug is raised, and the flow rate of the liquefied gas may be increased continuously, and the flow rate of the liquefied gas may be decreased continuously as the plug is lowered on the other hand. Also, the liquefied gas flows through a plurality of slit portions and is divided into a plurality of string shaped flows, therefore, an impact shock due to a collision of the liquefied gas with the liquid surface of the beverage in the container is eased when the liquefied gas flows. Accordingly, the liquefied gas is prevented from spattering out of the container.
As a canned product filled with the aforementioned beverages, on the other hand, a demand for the use of a bottle-shaped can is increasing in recent days. The bottle-shaped can, as disclosed in the specifications of U.S. Pat. Nos. 5,718,352, 6,499,329, 6,463,776 and so on, is a metal can of which a diametrically small threaded neck portion, inclining shaped shoulder portion, and thin plated diametrically large cylindrical trunk portion are formed integrally. In case of dispensing the liquefied gas into the container of this kind through the aforementioned nozzle, the problem to be described hereafter could occur, because the opening diameter (20 mm to 30 mm) of the bottle-shaped cans is smaller in comparison with that (51 mm to 64 mm) of the ordinary drawn and ironed cans (DI cans) according to the prior art.
Namely, it is necessary for the width or the sectional dimensions of the flow path of the liquefied gas flowing out of the nozzle to be narrowed in accordance with the opening diameter of the bottle-shaped can, in order to dispense the liquefied gas flowing out of the nozzle into the bottle-shaped can as efficiently as possible. For that purpose, a diameter of the nozzle, and a diameter of the cylinder and the plug which construct a nozzle have to be made small. If so, as shown in FIG. 14 for example, the flowing condition of the liquefied gas Lg from the liquefied gas dispensing nozzle Nz is divided into string shape in the same number of the slit portions Gr of the cylinder Cy, directly underneath the nozzle Nz. However, a plurality of the string-shaped flows get gradually closer and interflow into a unified flow in the end, due to the inclination of the slit bottom of the slit portions Gr toward the center. Accordingly, the impact of the liquefied gas Lg becomes big when it is fallen onto liquid level in the can, and the liquefied gas Lg is spattered due to big rebound on the liquid level in the can. Thus, a wide variation in an internal pressure in each can after being sealed may result.
Moreover, according to the liquefied gas dispensing apparatus of the prior art, as disclosed in the specifications of U.S. Pat. Nos. 4,471,627, and 4,703,609 for example, a movable portion (a valve or etc. for opening and closing a nozzle hole) of the liquefied gas flowing nozzle is fixedly joined to the lower end of a rod which penetrates a liquefied gas reserving tank in longitudinal direction from above, the rod is moved vertically so that a movable portion of the nozzle is moved vertically thereby to open and close the nozzle.
In the liquefied gas flowing nozzle which is composed mainly of the cylinder and the plug as disclosed in the aforementioned Japanese Patent Laid-Open No. 10-250711, the flow rate of the liquefied gas is also changed with varying a raising position of the plug by means of controlling an upward moving range of the rod, together with opening and closing the nozzle by means of moving the rod vertically, with joining the plug as a movable portion of the nozzle fixedly to the lower end of a rod which passes though a liquefied gas passage being communicated with the liquefied gas reserving tank in a longitudinal direction from above.
Thus, in the liquefied gas dispensing apparatus which comprises a flowing nozzle or a dropping nozzle of the liquefied gas consisted of the cylinder and the plug, or a flowing nozzle or a dropping nozzle of the liquefied gas composed mainly of the cylinder and the plug, the installing position of the rod for moving the plug vertically and the installing position of the cylinder are aligned on a common axis, in order to allow the plug which is joined to the lower end of the rod to be inserted into the cylinder from above.
However, in case the axes of the rod and the cylinder are not accurately congruent with each other due to a slight misalignment of both installing positions, or due to a slight inclination of the rod, the plug is slightly inclined to the cylinder when the plug is inserted into the cylinder.
As a result, lopsided force is acted between the outer circumferential face of the plug (an outer circumferential face of a rod shaped plug portion) and an inner circumferential face of the cylinder (an inner circumferential face of a cylinder hole). In consequence, a phenomenon called galling is generated and this makes the plug inserted in the cylinder hard to move. When galling is generated, there is a possibility for the plug not to move vertically in a predetermined distance, even if the rod is driven with a predetermined driving force. Also, a problem such as deterioration in a sealing performance could occur, due to a degrading of closeness at a contact portion between the cylinder and the plug when the nozzle is closed.
Furthermore, the liquefied gas dispensing apparatus according to the prior art controls opening and closing of the valve of a liquefied gas feeding conduit communicating a primary tank of the liquefied gas and the reserving tank, based on the detection result of a height of the liquid level of the liquefied gas in the liquefied gas reserving tank which is detected by two fluid level sensors, as disclosed in the aforementioned specification of U.S. Pat. No. 4,471,627. Namely, the valve is opened as a result of detection of a first liquid level sensor that the liquid level falls to a predetermined level. And then, the valve is closed when a second liquid level sensor detects that the liquid level rises to a predetermined level. Thus, the height of the liquid level in the reserving tank is maintained generally constant by means of executing and suspending the feeding of the liquefied gas to the reserving tank from the primary tank.
However, the temperature of the liquefied gas fed from the primary tank is extremely low such as −196° C. in case of liquid nitrogen for example, so that the liquid nitrogen vaporizes partially as it passes through the feeding conduit and the liquid nitrogen being fed is pressurized when it enters the reserving tank. Consequently, the liquid nitrogen collides with the liquid level so hard and thereby the liquid level may be waved or vibrated significantly. If the liquid level waves or vibrates significantly, the liquid level sensor decides that the liquid level rises higher than the actual level and an erroneous detection of the liquid level arises. As a result, a complementary amount of the liquid nitrogen becomes smaller or inaccurate, therefore, the liquid level cannot be kept within the predetermined range in the reserving tank. Accordingly, it is possible to generate a big difference in the amount of the liquefied gas to be flown or dropped from the nozzle by means of its own weight.